In recent years, there have been many types of optical disks distributed. FIG. 1 shows an example of such optical disks. The optical disk 10 shown in FIG. 1 is made of a resin that is transparent to the wavelength of the readout beam. Its typical diameter is 120 mm and the thickness is 1.2 mm. If the optical disk 10 is a CD, the information is recorded on the side opposite to the transparent surface (i.e. the readout surface) from which the information is to be read out. If it is a DVD, the information is recorded on a layer located at a depth of about 0.6 mm from the readout surface.
The recorded information can be read out by casting a laser beam through the readout surface onto the information layer and detecting the beam reflected by the information layer. Therefore, if a scratch is present on the readout surface, the information cannot be correctly read out because the readout beam is scattered or blocked by the scratch.
Presence of a scratch on the readout surface does not damage the information itself because the actual information is not recorded on the readout surface. Accordingly, removal of the scratch by polishing the readout surface has been carried out to restore the optical disk 10 so that the information can be read out again.
The planer area on which the recorded information is located extends from 22 to 58 mm in the radial distance from the center of the optical disk 10. Therefore, in the process of polishing the readout surface, it is particularly necessary to evenly and smoothly polish this area of the readout surface (i.e. the shaded area 10A in FIG. 1(A). This shaded area 10A is called the polishing area hereinafter).
An example of conventional optical disk restoration devices is shown in FIG. 2, which is a side view schematically showing the construction of the conventional optical disk restoration apparatus.
The optical disk restoration apparatus shown in FIG. 2 includes a disk rotating controller for rotating the optical disk 10 and a polishing body rotator for holding and rotating the polishing body.
The disk rotating controller includes: a turntable 22 having a shaft 21 as the rotation shaft, on which the optical disk 10 is to be set; a bearing 23 providing a rotatable support of the shaft 21; and a rotating controller 28 for regulating the rotation of the turntable 22.
The polishing body rotator, which is located over the disk rotating controller, includes a polishing body holder 26 for holding the polishing body 25 via an attaching/detaching means 24, a motor 27 for rotating the polishing body 25, and a pressing mechanism (not shown) for pressing the polishing body 25 onto the optical disk 10 with a predetermined pressure required for polishing.
In the conventional optical disk restoration apparatus having the above-described construction, the optical disk 10 is rotated around the shaft 21 in one direction, and the polishing body 25 being pressed onto the optical disk 10 is rotated in the same or opposite direction. Meanwhile, the rotating controller 28 regulates the rotation of the optical disk 10 so that a speed difference or speed ratio appropriate for the polishing process takes place between the two elements 10 and 25. This causes friction between the optical disk 10 and the polishing body 25, so that the (readout) surface of the optical disk 10 is polished by the polishing body 25.
In this optical disk restoration apparatus, the center of the polishing body 25 is located in proximity to the outer circumference of the optical disk 10 (in the present case, it is located inside the circumference, which can be outside the circumference) in order to polish the polishing area 10A. Therefore, the polishing body 25 operated by the pressing mechanism is mainly pressed onto the area close to the outer circumference of the optical disk 10.
However, when the pressing, i.e. the pressure is centered in proximity to the outer circumference of the optical disk 10, the pressing force is unevenly distributed within the polishing area 10A. This may be due to the rigidity of the turntable 22 or polishing body holder 26, which is high at the center but lower at the points closer to the circumference, or due to some structural looseness present per se in the disk rotating controller or the polishing body rotator. This results in a situation where a high level of pressure acts on the outer area of the optical disk 10 whereas its inner area receives only the lowest level of pressure. If this occurs, the area receiving the high pressure is excessively polished, whereas the area receiving the lowest pressure is inadequately polished.
To produce a substantially uniform distribution of the pressing force within the polishing area 10A, an apparatus shown in FIG. 3 has been proposed. In the optical disk restoration apparatus shown in FIG. 3, the polishing body rotator 31 and/or the disk rotating controller 32 is inclined inwards (i.e. toward the center of the apparatus) by a predetermined angle to decrease/increase the pressing force working on the outer/inner area of the optical disk 10.
However, the above-described construction, in which the polishing body rotator 31 and/or the disk rotating controller 32 is to be inclined, requires a mechanism for inclining the aforementioned mechanism 31 or 32 and also a regulating mechanism for adjusting the inclination to a predetermined angle. As a result, the apparatus becomes more complex, which is accordingly larger and more expensive.
In the above-described optical disk restoration devices shown in FIGS. 2 and 3, the polishing process is performed with a single polishing body. On the other hand, it has already been a general practice to use multiple types of polishing bodies differing in fineness and/or softness, particularly in order to effectively remove deep scratches. One example is the mirror polishing technique, in which a rough polishing process using a sandpaper-like polishing body is performed, which is followed by another polishing process using a polishing liquid (“compound”) and a polishing body made of cloth or sponge (“buff”).
FIG. 7 shows an example of conventional optical disk restoration devices using multiple polishing bodies. FIG. 7 is a plan view of the conventional optical disk restoration apparatus (A) and a side view (B).
The optical disk restoration apparatus shown in FIG. 7 mainly consists of a disk rotating controller 70 for rotating the optical disk 10 and a polishing body rotator 71 for holding and rotating the polishing bodies.
The disk rotating controller 70 includes a turntable 702 having a shaft 701 as the rotation shaft, a bearing 703 providing a rotatable support of the shaft 701, and a rotating controller 704.
The polishing body rotator 71, which is located over the disk rotating controller 70, includes a turret 712 for holding multiple (four in the present apparatus) polishing bodies 711, a turret driver (not shown) for rotating the turret 712, and a motor 713 for rotating the polishing body 711. In the turret 712, the polishing body 711 is fixed to a rotatable shaft 714 supported by a bearing (not shown). The shaft 714 is provided with driven gears 716, which is to be engaged with a drive gear 715 linked to the motor 713. The driving force of the motor 713 is transmitted through these gears 715 and 716 to the shaft 714 of the polishing body 711.
The polishing body rotator 71 and/or the disk rotating controller 70 includes an elevator (not shown) for vertically moving the polishing body 711 and/or the optical disk 10 so that the polishing body 711 and the optical disk 10 are pressed onto each other or separated from each other.
The conventional optical disk restoration apparatus having the above construction operates as follows:
First, the operator mounts an optical disk 10 on the turntable 702. At this moment, the mounted optical disk 10 and the polishing body 711 are out of contact with each other.
After the optical disk 10 is mounted, the turret driver rotates the turret 712 so that one of the driven gears 716 is engaged with the drive gear 715. Which of the four driven gears 716 is to be engaged with the drive gear 715 is determined depending on the depth of the scratch on the surface of the optical disk 10. For a deep scratch, the driven gear 716 fixed to the shaft 714 of a coarse polishing body 711 is brought into engagement with the drive gear 715. For a shallow scratch, on the other hand, the driven gear 716 fixed to the shaft 714 of a fine polishing body 711 is brought into engagement with the drive gear 715.
After one of the driven gears 716 is engaged with the drive gear 715, the elevator of the polishing body rotator 71 and/or the disk rotating controller 71 produces a vertical force to press the polishing body 711 and the optical disk 10 onto each other.
After the pressing operation, the motor 713 is activated to rotate the polishing body 711. Alternatively, it is possible to start the rotation of the polishing body 711 before the pressing operation is started. Meanwhile, the rotating controller 704 is also activated to rotate the optical disk 10. It is also possible to make the optical disk 10 passively rotate due to the reaction force resulting from the rotation of the polishing body 711. In this case, the rotating controller 704 regulates the rotation of the optical disk 10 so that a speed difference or speed ratio appropriate for the polishing process takes place between the two elements 10 and 711.
Thus, friction is caused between the optical disk 10 and the polishing body 711, whereby the surface of the optical disk 10 is polished by the polishing body 711.
After the above polishing process is finished, the elevator produces a vertical force to separate the polishing body 711 and the optical disk 10 from each other, and the rotation of the motor 713 and the rotating controller 704 is stopped.
Subsequently, the driven gear 716 (i.e. the polishing body 711) to be engaged with the drive gear 715 is switched to a new one, and the above-described sequential operations are performed again. If the previously used polishing body is the coarse type 711a, a fine polishing body 711b should be hereby used. If the previously used polishing body is the fine type 711b (including the case where the fine polishing body 711b is used after the coarse type 711a), a finer polishing body 711c for the finish polishing should be hereby used. After the polishing body 711c is used for the finish polishing, a polishing liquid (compound) and a polishing body (buff) 711d for mirror polishing should be used. After the mirror polishing process is performed as described earlier, the optical disk restoration process using the present apparatus is totally finished.
In the conventional optical disk restoration apparatus constructed and operated as described above, when the elevator is activated to press the polishing body 711 and the optical disk 10 onto each other, all of the four polishing bodies 711 held by the turret 712 come closer to the optical disk 10. Therefore, as shown in FIG. 7, it is necessary to position the center (or rotation shaft) of the turret 712 outside the circumference of the optical disk 10 so that only a proper polishing body 711 is pressed onto the optical disk 10 in each stage of the above-described restoration process. However, such a positioning of the turret 712 relative to the optical disk 10 makes the restoration apparatus larger and accordingly increases the production cost.
To solve the above problem, the present invention intends to provide an optical disk restoration apparatus that is simple structured and small sized to reduce the production cost, that can evenly apply the pressing force, and that is capable of performing a polishing process in which only a proper polishing body is selected from multiple polishing bodies and pressed onto the optical disk in each stage of the optical disk restoration process.